It has been shown that intravascular stents are an excellent means to maintain the patency of blood vessels following balloon angioplasty. As stent technology has advanced, more and more complex anatomy has been treatable with stents. A particularly difficult anatomy to treat is that of a bifurcation in a blood vessel at the ostium of a side branch.
Fischell et al., U.S. Pat. No. 5,749,825, describes a stent system for bifurcations. The Fischell design has two guide wire lumens allowing the deployment of a stent in the first blood vessel while leaving a guide wire positioned through the stent struts into the second vessel which is a side branch.
The Fischell design needed several modifications for universal use. First, by needing two guidewires, the profile (outside diameter) of the stenting system is significantly larger as compared to a stent delivery catheter that uses a single guide wire. Second, the Fischell design does not address placing a stent into the second branch across the ostium, which is often not at a 90-degree angle to the first vessel.
A bifurcation stent delivery catheter with two distal balloons and one stent segment for each of the two vessels would give the capability of stenting the second branch vessel, but such a device would be larger in profile and harder to deliver than the Fischell device. If one places a first stent into a main artery with that stent being positioned across the ostium of the side branch, and the side branch is not at a 90-degree angle to the main branch, then either the second stent will extend into the main branch of the artery or some portion of the arterial wall at the ostium will not be properly supported by the second stent.
Most current tubular stents use a multiplicity of circumferential sets of strut members connected by either straight longitudinal connecting links or undulating longitudinal flexible links. The circumferential sets of strut members typically are formed from a series of diagonal sections connected to curved sections, so as to form a circumferential, closed-ring, zig-zag structure. This structure opens up as the stent expands to form the elements of the stent that provide structural support for the arterial wall. A “single strut” member is defined for use herein as a diagonal section connected to a curved section within one of the circumferential sets of strut members.
The terms “side branch” and “bifurcation” will be used interchangeably throughout this specification.